Continuity mistake: In the final battle, Wasp and Ant-Man are in the van trying to get the quantum tunnel operational. We cut back to the fight and we can see Ant-Man there too, fighting in his giant form. (02:22:20 - 02:23:00)
Factual error: Gorillas are almost exclusively herbivores. They have been observed eating small insects and grubs but nothing larger. So why does Isabelle eat a rat at the beginning of the film? The serum may have turned her into a crazed killer, as it does with Sebastian, but it hasn't changed the structure of her teeth and palate, biochemistry of her digestive system and so on, all of which would be required. She might kill or torture the rat, but she'd never eat it.
Factual error: Twice in the film it is made clear that the Pym particle works by reducing the space between atoms in order to shrink an object, and by increasing it to enlarge them. This means that the object will weigh the same, whether shrunk or enlarged - it cannot be otherwise. A 90kg man the size of an ant would punch a hole through any surface upon which he stood (and couldn't ride ants), Doctor Pym has been walking about with a 60 tonne tank in his pocket, Darren Cross lifts a full grown sheep between finger and thumb, and the supersized Thomas The Tank Engine would be far too light to crush the police car (in fact it would float harmlessly away as it would probably weigh less than the air it displaced).
Other mistake: In the slaughterhouse scene, after Harrigan has injured the Predator with his shotgun and Keyes reappears, the Predator throws its disc, and severs Keyes in half at the waist. We see his legs flop to the ground, and blood pour from above, but his upper half (torso, backpack and weaponry) mysteriously remain hovering out of sight. (According to the director, the MPAA made him cut the footage of the top half of his body hitting the ground because it was too gory, creating this odd error). (01:21:50)
Factual error: Listening to a radio broadcast, live, since no other indication is given, Joe Louis is completing the 12th round of a fight. This is December 6, 1941. Joe's last fight of 1941 occurred in September, his next fight was January 1942. (00:00:10)
Continuity mistake: On the ferry, Rachel wears the purple/pink camouflage hoodie over her orange knit sweater with the colorful stripe sleeves, as usual. Now this is where things become strange. In the first shot as the trio come ashore, she is only wearing her orange sweater, she is not wearing the purple/pink hoodie - note the clear lack of fur hood. In the very next shot as they climb a bit more and then rest, Rachel is wearing the purple/pink hoodie - note the hood, but now it's on under her orange sweater. In the underwater shots she is also wearing it under the orange sweater. (This odd mistake has absolutely nothing to do with the very long wool cloak that Rachel wears in the next scene). (01:02:20 - 01:04:40)
Factual error: When the bus is shown entering Washington, DC for the competition, the shot shows the bus traveling over the Arlington Memorial Bridge with the Lincoln Memorial in the background. That bridge is on the southwest side of the city. Since NYC is to the northeast of DC, this means that to get to that bridge and enter DC that way, the bus had to drive all the way around the city and then come back in from the opposite direction. Even if the bus driver made a mistake and missed the most direct route into the city from the north, there are dozens of other ways to get to the heart of the city without adding a good 45 minutes to an hour to the trip.
Continuity mistake: In the latter half of the movie, Picard looks at a picture of himself from his days as a Starfleet Academy cadet while Beverly looks on too. This picture is actually the actor Tom Hardy (Shinzon, Picard's clone) and he appears with a completely bald/shaved head. Showing Picard bald as a cadet completely contradicts the TNG series. In the TNG episode 'Tapestry', a flashback set in 2327 (the year Picard graduated from the Academy), Picard is shown with a full head of hair. Also, in the TNG episode 'Violations', a flashback set in 2354 shows Picard with a partial head of hair when he takes Beverly to see her dead husband Jack's body. (00:46:25)
Visible crew/equipment: When C-3PO is on the conveyor belt, if you look in the reflection in his head you can see the camera crew. (01:26:40)
Continuity mistake: When the Senator is about to be sacrificed, the cloth on her mouth immediately disappears for a split second. (01:29:35)
Continuity mistake: It was briefly stated in the second film that the T-Virus was created by Dr. Ashford to cure his daughter Angela and that the Red and White Queens were based on her. This movie contradicts that by suggesting that Dr. Marcus created the T-Virus to cure his daughter Alicia, and that the Red/White Queens were modeled after her. While the rest of the movie stays true to the continuity of the previous films, this rather obvious ret-con is still a major continuity gaff.
Continuity mistake: Dick Jones brags (admits?) to Robocop, "I had to kill Bob Morton because he made a mistake. Now, it's time to erase that mistake" while Robocop is crouched on the ground, not only looking away from him from across the room, but also Robocop's eyes are in a vertical position. In the playback, Jones is facing the camera as though it were videotaped or filmed in a studio. (01:10:50 - 01:35:10)